The major goal of the present program is the evaluation of drugs that might be effective in suppressing or reversing atherosclerosis. The investigation is being carried out in both rabbit and monkey in which atherosclerosisis is being produced by feeding a high cholesterol diet. Studies with a number of drugs including colchicine, aspirin and dipyridamole suggest that these drugs, in the presence of marked hypercholesterolemia, have no significant protective effects on the development or progression of experimental atherosclerosis. However it is possible that these and other drugs may be effective when they are administered with a low cholesterol diet. This approach is currently under investigation.